1. Field of the Invention
The present invention relates to a mirror device for a vehicle and to a retracting mechanism of an outer mirror device for a vehicle, which are provided at a vehicle.
2. Description of the Related Art
Among door mirror devices for vehicles, there are those which are provided with a retracting mechanism (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2002-67805). Such a retracting mechanism has, for example, a supporting shaft. The supporting shaft is fixed to a vehicle body. Within a case member (which will be described hereinafter), a second helical gear is provided at the supporting shaft in a state in which rotation of the second helical gear is impeded.
The retracting mechanism has the case member, which is supported at the supporting shaft so as to be freely rotatable. A mirror for viewing the region toward the rear of the vehicle is connected to the case member. The case member is always rotated integrally with the mirror.
A motor is fixed within the case member. A first worm gear is provided at the output shaft of the motor. A twin gear is provided within the case member. The twin gear has a first helical gear and a second worm gear. The first helical gear is meshed with the first worm gear. Due to the first helical gear being rotated by rotation of the first worm gear by the driving of the motor, the twin gear is rotated, and the second worm gear is rotated integrally with the first helical gear. The second worm gear is meshed with a second helical gear. Due to the second worm gear being rotated, the second worm gear is rotated around the second helical gear. In this way, the case member is rotated around the supporting shaft, and the mirror is retracted or extended.
However, in this door mirror device for a vehicle, the first helical gear and the second worm gear of the twin gear are integral. Therefore, when load is applied from the first worm gear to the first helical gear, or when load is applied from the second helical gear to the second worm gear, the second worm gear is affected by the tilting of the first helical gear, and the second worm gear tilts integrally with the first helical gear. Further, the first helical gear is affected by the tilting of the second worm gear, and the first helical gear tilts integrally with the second worm gear.
Accordingly, there is the problem that the sound of the operation changes between when the twin gear is rotated in one direction and the mirror is retracted, and when the twin gear is rotated in the other direction and the mirror is extended.